Movement monitoring systems are available in which for example tags are attached to article, which tags are then detected, if the article is moved past a predetermined location. Such systems are well known as shoplifting prevention systems in stores.
However, those systems are unsuitable for use in detecting the movement and individual identity of an object or person, or for identifying that object or individual from others. In many cases, including industrial processes, luggage handling, movement of transport or rail cars, military applications, in animal care, and in institutions and large commercial organizations, it is desirable to monitor movement of units which may be inanimate objects, mobile units, animals or persons, and in particular to instantly detect the identity of such a unit when movement is detected. In the particular case of hospitals, it is desirable to monitor movement of individuals from one area to another in the building, or at entrances and exits to the building.
In these cases it is not enough simply to detect movement. It is essential to be able to detect both that movement has taken place, and it is also necessary to immediately identify the person or unit detected.
Different action may be required depending upon the identity of the person or unit detected.
For example, in the case of a hospital, it may be highly desirable to detect movement of hospital staff such as doctors, nurses and the like from one area to the other in the building, so that their location may always be known. This greatly facilitates paging of hospital staff in the case of an emergency for example. However, in the case of hospital staff it is not normally necessary to take any remedial action.
Conversely, in the case of patients in hospitals, it is necessary not only to detect movement of a patient into or out of a building or an area within a building, but it may also be necessary to immediately institute some form of remedial action such as instituting a search, or sending out hospital staff to locate the patient, and if necessary to see that the patient returns to the location where he is supposed to be. Clearly, this type of monitoring may be required in many other types of buildings and institutions, the case of the hospital simply being the most familiar example.
In the case of livestock rearing, it has been proposed, in U.S. Pat. No. 4,274,083 to provide each animal with a transmitter, receiver, battery, and antenna, and to provide a monitoring location in an agricultural building, which will then provide information concerning the individual animal.
However, in this system the transmitter, receiver, battery package which is attached to the animal is relatively massive, and the system requires that the animal transmitter and receiver shall be "on" at all times.
This will, of course, result in a fairly rapid depletion of the charge in the battery, which will then mean that each individual unit must regularly be recharged in order to maintain the entire system operational.
These factors render the system unsuitable for identification of units or persons, particularly in the case of patients in hospitals. Clearly, it would be unacceptable to require each patient to wear a relatively massive structure such as that shown in the patent referred to.
However, it is well known that hospital procedure requires that each patient shall wear an identification bracelet or wrist band usually made of plastic, and in the majority of cases being disposable.
In many of the other applications referred to, identity labels or tags are used on units, which are also particularly suited to use in conjunction with the invention.